This invention relates to stowable and deployable structures useful for antenna and solar cell arrays, and particularly to such structures which are useful in the context of space vehicles.
A recurring problem associated with spacecraft is that of stowing the complete spacecraft in a transport vehicle or booster for transport of the spacecraft from the Earth's surface into space, and upon its arrival in space deploying the structures of the spacecraft into a usable configuration. This problem comes about because vehicles adapted for lifting a load from the earth's surface into an orbit require a streamlined shape because of aerodynamic considerations. For example, unmanned booster vehicles ordinarily carry their payload in a fairing or tapered nose cone. The space shuttle bay is more nearly cylindrical in form, but is limited both in length and diameter. Ordinarily, spacecraft structures such as antennas, sensing instruments and probes, and solar panels are collapsed to dimensions within an envelope which will fit within the limitations of the boost vehicle, and are then unfurled or extended in space.
Advancing levels of technology tend to require larger solar panels because of greater power demands, and larger and more complex antenna structures for generating directional antenna beams. Parenthetically, it should be noted that the term antenna beams refers to beam shaping in both transmission and reception modes, both modes of operation being understood even though only one mode is mentioned. The requirement for larger deployed structures can be fulfilled by larger boost vehicles or by advanced stowing and deployment techniques. The use of larger boost vehicles may not be possible because such vehicles are unavailable, cannot be scheduled, or are too expensive.
In general, the performance of an antenna depends upon its configuration or shape as well as upon its size. A large antenna array will not operate properly if its deployed configuration does not meet its planar flatness or its dimensional accuracy requirements. Furthermore, the deployed antenna should resist changes in its configuration or dimensions attributable to temperature or external forces to which it may from time to time be subjected. Thus, rigidity and dimensional stability are among the desirable attributes of a deployable antenna. Among the known types of deployable antennas are the array antennas, in which the array is supported on a plurality of panels which are folded for stowing, and unfolded into the desired configuration. The stowed volume of an array antenna comprised of panels depends upon the deployed area of the panels, and also on the thickness of the panels. In order to reduce stowed volume for a given deployed area, it would appear that one could merely reduce the thickness of the panels. The reduction of thickness, however, reduces the ability of the deployed structure to resist deformation. An improved antenna structure is desired.